You don’t know these names, but you should. Everyone should. They’re bona fide American heroes who dedicated their time and energy to protecting not only our country, but also every soldier in the Allied forces during World War II. And they did so when they should have otherwise been continuing their collegiate studies.

That’s right, these women who came from majors as diverse as botany, math, psychology, and English, were recruited out of college in order to build a dedicated code-breaking unit for the US armed forces.

It all started in early 1942, as secret letters began showing up in college mailboxes. Schools like Bryn Mawr, Mount Holyoke, Barnard, Radcliffe, and more posed two questions to prospective female recruits:

1. Did she like crossword puzzles?
2. Was she engaged to be married?

All of these women replied yes, they like crossword puzzles, and no, they’re not engaged or soon-to-be engaged.

After answering these questions, the women began attending introductory meetings. They were issued manila envelopes containing “a brief introduction to the arcane history of codes and ciphers, along with numbered problems sets and strips of paper with the letters of the alphabet printed on them.”

Each packet contained one problem that could not be solved, to show that sometimes, a jumble of letters or numbers doesn’t stand for anything. Sometimes, gibberish remains just that, because sometimes a code-breaker fails.

They developed working knowledge of foreign languages they didn’t speak. They memorized the most common English letters — E, T, O, N, A, I, R, S — and took frequency counts.

And that’s how America built its answer to England’s Bletchley Park code-breaking operation. (The American effort, known as Arlington Hall, was considered by their Bletchley Park rivals as “just a lot of kids playing at ‘office’.”)

College presidents like Ada Comstock, the president of Radcliffe College (the women’s counterpart to Harvard), were recruited to identify candidates to learn cryptanalysis to help shorten the war.

And make no mistake, they did shorten the war. They helped crack Enigma, which was key to decimating the German U-boat fleet, and their code-breaking efforts were instrumental in defeating Japan as well, providing valuable intel on the island-to-island battles of the Pacific theater.

Of the US Army’s World War II code-breaking force, nearly 70 percent was female. We’re talking 7,000 female code-breakers. When you factor in US Navy recruits as well, that number jumps to 11,000 women out of 20,000 code-breakers.

From Code Girls: “Code breaking required literacy, numeracy, care, creativity, painstaking attention to detail, a good memory, and a willingness to hazard guesses. It required a tolerance for drudgery and a boundless reserve of energy and optimism.”

Genevieve Grotjan was key to cracking the Japanese cipher known as Purple, and William Friedman, the man who initially ran the Arlington Hall operation, described the Purple cipher as “by far the most difficult cryptanalytic problem successfully handled and solved by any signal intelligence organization in the world.” He specifically pointed to the contrbutions of Grotjan, Mary Louise Prather, and other women in the Arlington Hall group.

Codes used by twenty-five different nations were analyzed by Arlington Hall, including codes of friends and foes alike. “There was a French code called Jellyfish, a Chinese enciphered code they called Jabberwocky, another they called Gryphon.”

But even their staggering efforts in code-breaking weren’t all they contributed to the cause. They were also crucial to the success of the D-Day invasion, as many of the women were put to work reverse-engineering messages in order to create false information about imaginary troop movements and landing areas. And in order to create fake signal traffic, they had to know the real traffic backward and forward.

I could go into more detail, breaking down how they cracked some of the war’s most important code languages, or exploring their personal lives and how life changed for these college students-turned-military operatives, but I don’t want to reveal more than I have already.

Read Code Girls. You won’t regret it. It’s another terrific entry in a year of books full of revelations about wartime puzzle history. We’ve been taken behind the scenes of the NSA, Bletchley Park, and now Arlington Hall.

And once more, important and influential female voices are getting the limelight far later than they deserve. It’s about time.

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